This invention relates to television camera registration systems for insuring the registration of the individual rasters developed by multiple image pickup devices.
Present day television cameras may include two or more image pickup devices for developing video signals representative of a scene being viewed. In television cameras of the multiple image pickup device type, each image device has associated means in the form of deflection components and deflection signal generators for developing a related raster signal. Although a great amount of effort is expended in the mechanical and physical alignment and the selecting or matching of the image pickup devices for deflection sensitivity, as well as the deflection components and their associated waveform generators, it is virtually impossible to achieve the desired registration or overlap of the individual rasters from each image pickup tube without some means of making fine adjustments for raster parameters, such as centering, width, height, linearity, skew and rotation of one raster relative to another raster with reference to a common scene projected optically within the same camera.
Camera systems have been developed which provide for both local and remote normal control of the aforementioned parameters; however, such adjustments are time consuming and require frequent re-adjustment in order to maintain satisfactory registration of the individual rasters in a multiple image pickup device television camera.
Automatic registration systems are therefore desirable and such systems have been developed. Generally, the method of operation of the known automatic registration systems involves developing an output video waveform from each image pickup tube, for example, by viewing a test chart and comparing the phase or time displacement of the resultant video waveforms.
The conventional phase detector, generally in the form of a level comparator circuit, compares the rising video waveform with a reference voltage level to determine the position of one raster related video signal with regard to the other raster related video signals; that is, the leading or trailing edges of the video waveform are determined, compared and an error signal generated related to the displacement of the video signals. However, the typical video waveforms from image pickup devices viewing a test chart pattern or scene are not normally identical, since the video waveforms do not represent the ideal square wave response but, rather, waveforms which rise to a peak amplitude with significantly differing rising and trailing amplitude delays.
A conventional detector is therefore unable to accurately determine the required peak video amplitude point of each raster related signal by determining coincidence of the leading or trailing edges of the multiple video waveforms.
More elaborate detectors have been developed in which multiple samples of both the leading and trailing edge crossovers with respect to a specific reference pattern are taken, and by means of an electronic computer and an elaborate software program, a determination of the peak amplitude is made for determining the difference between the raster related video waveforms.
The automatic registration systems, as described above, have not been widely accepted, because although the adjustments are made automatically, the means for detecting the misregistration of one raster relative to another either does not have a sufficient degree of accuracy; or in the case of the more elaborate detectors, the increased complexity and cost of the automatic raster registration systems is not warranted.